Method for improving steel and steel sheets



' 15 commercial nature.

Patented Oct. 12, 1937 I 2,005,400 PATENT OFFIC STEEL SHEETS METHOD FORIIWPROVING STEEL AND Charles A. Scharschu, Brackenridge, Pa., assignorto Allegheny Steel Pennsylvania Company, a corporation of No Drawing.Application June 21, 1935,

' Serial No. 27,748

6 Claims.

l I My present invention relates to a process and, an alloy compound forimproving the properties of steel and steel sheets and more especiallyfor eliminating seams from steel and off-color areas from polished steelsheets. The present application is a continuation in part of anapplication filed by me on Dec. 19, 1931, under Ser. No. 582,177.

It is well-known that many stainless steel alloys and articles ofmanufacture fabricated therefrom are today used for ornamental purposes.This use *of stainless steel and stainless steel sheets has found widerand wider adaptation particularly in modern constructions both ofdomestic and of For such purposes, it is apparent that the appearance ofthe steel and steel sheets must not only be attractive physically butmust be uniform. Many such products have, however, been observed toexhibit defects which 20 either mar their appearance, limit theirapplication or prohibit their use for ornamental purposes. In somecases, these defects have actually prevented the use'of stainless steelproducts for some types of installations or have resulted in the 25necessity for reworking the defective pieces to improve them. In othercases, the defects have caused relegation of these products to minor orinconspicuous locations. This necessarily results in an economic lossand at the same time increases the cost of acceptable stainless steelproducts for ornamental purposes.

It has been observed that these defects are gen- 7 erally of two types.The type of defect exhibited by stainless steel, e. g., rounds, is knownas a 5 seam and apparently consists of a relatively nar-,

row imperfection, depression ortrough which has comparatively littlewidth and depth but which has considerable length which may amount, insome cases, to several inches, more or 4 .less. The type of defectexhibited by polished steel sheets is what is known as off-color areas.

When these areas are present in the polished steelsheets spots orlocalized areas appear either darker or lighter than the remainder ofthe sheet.

45 Some of these oif-color areas are darker thanthe main body of thesheet when viewed at one angle .and lighter than the main body of thesheet when viewed at another' angle. As above pointed out, these defectslimit the use of ornamental 50 stainless steel and cause increased inprice.

It is believed by some that these ofi-color areas result from ascattering of light. If such is true there must be a physical defect inthe material 55 which causes such light-dispersive or light-refractivephenomena. It is also thought thatthese defects result from the type ofdeoxidizer used during the production of the steel because when certaindeoxidizers are used it is known 50 that the resulting steel contains arelatively large perfect material to be the products of deoxidation findtheir way into the steel and constitute foreign matter with respect totheir composition as compared to the steel. Metallurgists know that asmall portion of all deoxidizers which are added to slags pass into thesteel prior to effecting complete deoxidation of the steel. Inasmuch asdeoxidizers are invariably reducing in nature they exert a reducingeifect'upon metallic oxides present in the steel and frequently formnon-metallic compounds which are either very difficult or evenimpossible to remove. v

WhereI refer to stainless steel or stainless steel sheets, especiallypolished steel and steel sheets, I mean in particular such products ofthe socalled 18-8 type which contain about 18% chromium, about 8%nickel, low carbon-usually up to about .3%low sonim content, and withthe balance substantially all iron. I do not, however, exclude othertypes of. stainless steel 'or iron but on the contrary I particularlymean to include all such which are adaptable for ornamental purposes.

I have discovered that stainless steel sheets and rounds. made fromstainless steel can be produced which are substantially entirely freefrom the above noted and other defects and the production of such formsone of the objects of this invention.

Another object resides in adding to the slag during the production ofthe steel a certain alloy compound which results in the production ofsheets and rounds very substantially free. from the noted defects.

Another object is to bring about a peculiar reducing action during themanufacture of the steel by adding to the slags used in the normalrefining of the steel an alloy-compound of the nature hereinafter setforth.

A still further object is to produce stainless steel sheets and roundsof uniform high grade adaptable for ornamental use by a modifiedsteelmaking process.

, Other'objects and advantages are to reduce the slags used during thenormal manufacture of steel by means of an alloycompound composedprimarily of calcium and silicon, together with such other objects andadvantages as will be understood by those versed in this art.

a I am aware that finely divided silicon, e. g., as ferro-silicon, hasheretofore been used to reduce the slag commonly used in makingstainless steels together with the fact that several other reducing ordeoxidizing agents have been suggested or tried. My observations andexperience have been, however, that steels made by known methods allproduce material which is defective at least to some extent and'which,therefore, is not widely applicable to ornamentation. In particular,stainless steels made by known practice exhibit the foregoing defects,when polished or when turned down in a lathe, to a greater or lesserextent but to an extent suflicient to cause the rejection of anappreciable part of the steel for ornamental uses.

In contradistinction to the foregoing, I have discovered that if I addan alloy compound of calcium and silicon, as hereinafter more fully setforth, a highly improved steel results which is substantially entirelyfree from the seams and oiT-color areas mentioned above. My alloycompound containing calcium and silicon is added to the slags normallyused in steel making operations. Such slags are frequently composedchiefly of lime and silica to which fiuorspar has been added to renderthem more fluid. My calcium silicon alloy compound can be added to sucha slag or to other slags as will be pointed out hereinafter.

I find that my alloy compound may, like more conventional deoxidizers,be added to the slag during the latter part of the deoxidation period. Iprefer, however, to add the alloy compound to the slag at or near thebeginning of the deoxidation period. Thus, the alloy compound is presentand in contact with the slag throughout substantially the entiredeoxidation period which produces somewhat better and more completeresults than adding the alloy compound at or near the end of thedeoxidation period.

In order that my present invention and the manner of carrying it out maybe clear to those skilled in this art I have reproduced hcreinbelow thepertinent data concerning what will be called heat No. 18,010. Inaccordance with the following table, I added the materials specified inthe amounts set forth and at the times noted in the lefthand column.

Heat No. 18,010

cium silicide in finely divided condition. This condition may be reachedeither by grinding calcium silicide to a finely divided condition or bypreparing it, e. g., chemically by precipitation, directly in a finelydivided condition as will be understood by those familiar with thehandling of such materials. In its simplest form, my new alloy compoundis substantially calcium silicide with or without minor percentages ofextraneous but harmless materials and in such case may be closely enoughindicated by the chemical notation CaSlz.

I am not limited, however, to an alloy compound containing substantiallyonly calcium and silicon. I contemplate the substitution or replacementof at least a part of the silicon content by other suitable metals suchas manganese although I do not intend that manganese shall be the onlyreplacement metal. Other metals may be used for replacement purposesinstead of manganese where they have those properties andcharacteristics suitable for use in connection with the presentinvention. Silicon replacement may be proportionate to the atomicweights of the elements involved although I am not limited to only thistype of replacement. Where the silicon is replaced in part or in wholeby manganese or other elements, my alloy compound cannot be designatedby a simple chemical formula since it is more likely to be a complexassociation of a number of chemical compounds as will be understood bythose familiar with chemical reactions.

I have discovered, however, that the use of calcium silicide, or somemodification or derivative thereof as above indicated, enables me toproduce sheets and rounds which are substantially entirely free from thedefects above described. I wish it to be understood that while I haveindicated the addition of 140# of calcium silicide in the foregoingexample I am not limited to such a figure. The precise or even approxi-Time Remarks 7:00 A. M. Heat started 4:23 P. M. Slag removed 4:25 P. M.Added new slag containing 400;! of lime and 105# of fiuorspar 4:50 P. M.Added 10# of calcium silicide and 10# of lime to the new slag 5:00 P. M.Added 10# of calcium silicide and 10# of lime to the slag 5:10 P. M.Added l0# of calcium silicide and 10# of lime to the slag 5:20 P. M.Added l0# of calcium silicide and 20# of lime to the slag 5:30 P. M.Added 10# of calcium silicide and l0# of lime to the slag 5:40 P. M.Adlded 5# of calcium silicide, 5# of lime and 10# of fluorspar to the sag 5:50 P. M. Added 5# calcium silicide and 25# of lime to the slag 6:00P. M. Added l0# of calcium silicide and 10# of lime to the slag 6:10 P.M. Added 10# of calcium silicide and l0# of lime to the slag 6:20 P. M.Added l0# of calcium silicide to the slag Alloying additions added: 8:15P. M. Added l0# of calcium silicide and l0# of lime to the slag 8:25 P.M. Added 10# of calcium silicide and 10# of lime to the slag 8:30 P. M.Added 10# of calcium silicide and 10# of lime to the slag 8:45 P. M.Added 10;? of calcium silicide and 10# of fluorspar to the slag 8:53 P.M. Added 10;? of calcium silicide and 10# of lime to the slag From theforegoing example it will be apparent that the slag and vflux (lime andfiuorspar) together constituted 675# and that the total additions ofcalcium silicide amounted to 140 Thus, in this particular instance theweight of calcium silicide added amounted to approximately 20% of theweight of the slag and flux.

In the above example the calcium silicide utilized containedapproximately 20 to 30% of calcium and about 80 to 70% of siliconalthough the exact proportions may be varied somewhat above or belowthese figures without departing from the mate amount of calcium silicideor derivative which is to be used in any particular heat of steel mustnecessarily depend upon the severity, known or expected, of the defectslikely to be exhibited by the particular analysis of steel being made.The amount of calcium silicide or derivative to be used can, however, bereadily determined by a simple test or by trial and error. I employenough calcium silicide to at least overcome the defects above mentionedand preferably I add a slight excess thereover since such an excessexerts no harmful effects upon the steel and enll the elimination of allthe defects.

jects noted. Whether the use of calcium silicide according to myinvention produces products of deoxidation of an unusual nature suchthat they diffuse from the steel to the slag or whether the calciumsilicide in accordance with my invention results in some peculiar orunusual refinement of the steel in certain respects I am not positive,but,

as already stated, the practice of my invention in variably produces theresults sought.

As I have above stated my invention is not limited to the use of anyparticular slag and the example of lime and fluorspar has been givenmerely for exemplary purposes. I have found that since the slag ismerely a vehicle for carrying out certain chemical and/or physicalreactions which are necessary in the refining of steel my inventionoperates equally well with slags of other types or compositions. Forinstance, I have observed that if a slag composed of lime and alumina orlime and other suitable refractory oxides so proportioned as tov givethe desired fluidity are used in the manner known by those skilled insteel making, the objects of my invention are equally well accomplishedin connection therewith and the advantages noted still exist. I,therefore, Wish it to be understood that the composition of the slag isinconsequential insofar as my present invention is concerned, and I havefound that in general it is not possible to lay down a general ruleconcerning the proportional relationship between the amount of calciumsilicide or the like utilized and the weight of the slag and flux.

What I claim as new and desire to secure by Letters Patent is: r

-1. A process of making stainless steel free from seams and off-colorareas which comprises preparing a suitable molten bath under a slag,removing the slag, forming a new slag thereon, and adding calciumsilicide to the slag in sufiicient amount to make it possible to producestainless steel free from such seams and off-color areas, the calciumsilicide being added in small increments at leastsome of which areaccompanied by slag-forming additions.

2. A process of making stainless steel free from seams and ofi-colorareas which comprises preparing a suitable molten bath under a slag,removing the slag, forming a new slag thereon, and

adding calcium silicide to the slag in suflicient' amount to make itpossible to produce stainless steel free from such-.seams and off-colorareas,

ments and each such increment being added a relatively short period oftime after the preceding increment, the calcium silicide additions beinginterrupted at a suitable time while the requisite alloying additionsare made to the bath. H

3. A process of making stainless steel free from seams and off-colorareas which comprises preparing a suitable molten bath under a slag,removing the slag, forming a new slag thereon, and adding. calciumsilicide to the slag in sufficient amount to make it possible to producestainless.

steel free from such seams and off-color areas, and calcium silicidebeing added in small increments at least some of which are accompaniedby slag-forming additions, the calcium silicide and slag-formingadditions being interrupted while the requisite alloying additions aremade to the bath.

4. A method of making stainless steel products adapted for ornamentaluses and free from seams and off-color areas which comprises preparing asuitable molten bath under a slag, removing the slag and substituting aslag of lime and fluorspar,

promptly beginning the addition of relatively closely spaced" incrementsof calcium silicide, at least some of which are accompanied byslagforming materials, interrupting the additions to incorporatesuitable alloying ingredients in the bath, and resuming the calciumsilicide additions 'until a predetermined total amount has been added.

5. A process of making ornamental 18-8 sheets and rounds substantiallyfree from seams and offcolor areas. which comprises preparing a moltenbath of low carbon iron, removing the slag which forms thereon, addingmaterials including lime and fluorspar to form a new slag, periodicallyadding calcium silicide, lime and fluorspar to the new slag,interrupting the additions to make alloying additions ,of chromium andnickel and delaying resumption of the other additions until the alloyingadditions are assimilated by the bath.

6. A process of making chromium nickel stainless steel sheets and roundssubstantially entirely free from seams and off-color areas which com-'prises making up a molten bath of iron, removing 'slag therefrom, addingmaterials including lime and fiuorspar to form a new slag on the bath,incrementally adding calcium silicide and lime to the slag, occasionallyadding fiuorspar to the slag for slag control, adding alloying agentsand completing the additions of calcium silicide, lime and fluorspar,finishing the heat, forming it into ingots and manufacturing sheets androunds from such ingots. v

CHARLES A. SCHARSCHU.

the calcium silicide being added in suitable incre-

